The invention relates to improvements in methods of and in apparatus for counteracting the lack of balance of cyclically moving parts, particularly for counteracting the lack of balance of parts or groups or assemblies of parts which are caused to reciprocate (move back and forth), often at a high or very high frequency. Still more particularly, the invention relates to improvements in methods of and in apparatus for compensating for the lack of balance of one or more units or parts, such as unbalanced drives, which are set up to impart reciprocatory (back-and-forth) movements to components of machines, production lines or the like.
It is customary to mass produce rod-shaped smokers' products by forming a continuous rod which is advanced lengthwise along a predetermined path (e.g., along a horizontal or substantially horizontal path), and by repeatedly severing the leader of the advancing rod by a knife or another suitable cutter which forms part of a so-called cutoff and is caused to move across a selected portion of the path. In order to ensure that the cutter will make clean cuts across the advancing rod, at least that portion of the cutoff which directly supports the cutter is caused to move back and forth in and counter to the direction of forward movement of the rod and to cause the cutter to sever the rod while the cutter moves in the direction of forward movement and at the exact speed of the rod. Such cutoffs are utilized, for example, to subdivide a continuously moving filter rod into a file or row of discrete filter rod sections, filter plugs or filter mouthpieces of unit length or multiple unit length, or to subdivide a continuously moving tobacco-containing rod into plain cigarettes, cigarillos, cigars or like rod-shaped smokers' products of unit length or multiple unit length. Analogous cutoffs can be employed with similar advantage to subdivide a running continuous tube (such as a cylinder of cardboard or the like) into discrete tubes of unit length or multiple unit length.
In certain modern cigarette makers, a single cutoff or a group of discrete cutoffs can be set up to simultaneously sever two or more parallel continuous rods into rows or files of discrete rod-shaped smokers' products which are introduced into one or more packing machines or into one or more so-called tipping machines wherein (if the ultimate products are filter cigarettes) pairs of coaxial plain cigarettes of unit length are assembled with filter mouthpieces of double unit length to form therewith filter cigarettes of double unit length. Such filter cigarettes of double unit length are severed midway across their filter mouthpieces to yield pairs of filter cigarettes of unit length.
Reference may be had, for example, to commonly owned U.S. Pat. No. 5,135,008 granted Aug. 4, 1992 to Oesterling et al. for “METHOD OF AND APPARATUS FOR MAKING FILTER CIGARETTES”. Filter rod sections of double unit length can be supplied to the apparatus of Oesterling et al. by a machine of the type disclosed, for example, in U.S. Pat. No. 4,412,505 granted Nov. 1, 1983 to Häusler et al. for “APPARATUS FOR APPLYING ATOMIZED LIQUID TO A RUNNING LAYER OF FILAMENTARY MATERIAL OR THE LIKE”. The apparatus of Oesterling et al. can receive plain cigarettes from a so-called SE rod maker which is distributed by the assignee of the present application. A more recent version, known as SE 2 rod maker, turns out two rows of plain cigarettes which can be fed to a so-called MAX 2 filter assembler distributed by the assignee of the present application. This filter assembler is a filter tipping machine and is or can be of the type disclosed in the aforementioned US patent to Oesterling et al. The SE 2 rod maker can be of the type disclosed, for example, in commonly owned U.S. Pat. No. 4,893,640 granted Jan. 16, 1990 to Heitmann et al. for “MULTIPLE-ROD CIGARETTE MAKING MACHINE”.
The device which guides successive increments of a single continuous rod or of several parallel continuous rods through the severing or subdividing station is known as tube or ledger. This ledger is often provided with a slot which guides the cutter of the cutoff during actual severing of the running rod or rods. Reference may be had, for example, to British patent No. 1,556,267, to German patent No. 2 233 064 and to U.S. Pat. No. 4,534,232 granted Aug. 13, 1985 to Harrington et al. for “LEDGER FOR CUT-OFF DEVICES IN CIGARETTE MACHINES”.
In many instances, the drive which moves the ledger for the continuously running rod or rods and, in many instances, the cutter or cutters of the cutoff back and forth along a preselected portion (severing station) of the path for the rod or rods employs a crank mechanism. Such mechanism is unbalanced and, therefore, the drive includes or cooperates with a counterbalance, counterweight or counterpoise (hereinafter called counterpoise) which is caused to rotate with a rotary part of the mechanism. That portion of the ledger which flanks the path for the knife constitutes or acts not unlike a counterknife to enhance the quality of the severing action and to thus further ensure that the cutter can make clean cuts across the tubular wrapper as well as across the rod-like filler of each continuously running rod. The aforementioned slot of the ledger is located in a plane which is normal to the direction of forward movement of the rod or rods (i.e., at right angles to the axis or axes of the rod or rods).
If the unbalanced drive for the ledger is or includes a crank mechanism, a crank arm of such mechanism is pivotably affixed to the ledger to reciprocate the latter in synchronism with the knife holder. Such drives for the ledger have found widespread acceptance in the tobacco processing industry. It has been ascertained that a crank mechanism is highly satisfactory as a means for reciprocating the ledger in synchronism with the cutter or cutters of the cutoff in a cigarette making or filter rod making machine, as long as the frequency of reciprocatory movement of the ledger is below a certain upper threshold value. However, once the frequency of reciprocatory movements of the ledger exceeds such upper threshold value (e.g., in a machine which turns out 16,000 or more plain cigarettes per minute), the presently known systems which are intended to compensate for the lack of balance of the drive for the ledger cannot ensure adequate counterbalancing of a crank mechanism. The result is that the rotating or orbiting parts perform pronounced vibratory or oscillatory movements which entail excessive vibrations of the floor, the generation of highly unpleasant body-transmitted vibration (noise), adverse influencing of the neighboring system(s) including electrotechnical components, and/or others.
The situation is aggravated because the axis of rotation of the crank mechanism is not located in the plane of forward movement of the rod or rods. Such positioning of the axis of rotation is neither desirable nor possible for constructive and other reasons (such as because this would adversely affect the quality of the severing action), i.e., it is not possible (with heretofore employed compensating means) to adequately counteract vibrations of that frequency and intensity which develop when the frequency of reciprocatory movements of the ledger (and hence of the cutter or cutters) exceeds the aforementioned threshold value. On the other hand, it is highly advisable to adequately compensate for or counteract the vibratory or oscillatory movements which develop when the reciprocatory movements of the drive reach a frequency which is required in a modern high-speed production line for filter cigarettes and the like.
The just discussed problems cannot be solved, or cannot be adequately solved, by proposals which are described in the aforementioned British and German patents and in the aforementioned U.S. Pat. No. 4,534,252 to Harrington et al. Such prior proposals are satisfactory when the ledger is called upon to reciprocate within a certain range of frequencies but they cannot eliminate or adequately reduce the generation of noise, vibrations of the floor, undesirable stray movements of neighboring units and/or other undesirable phenomena attributable to the need for high-frequency oscillations of the ledger, of the cutter or cutters and of certain other parts such as those which impart movements to the ledger and/or to the cutter(s).